The production of 2-ethylhexanol (2EH) from normal butyraldehyde (NBD) is being industrially conducted on a large scale. This process is constituted of an NBD condensation step in which two molecules of NBD undergo aldol condensation and dehydration to give 2-ethylhexenal (ethylpropylacrolein, EPA), an EPA hydrogenation step in which the EPA obtained is reacted with hydrogen to obtain crude 2EH, and a 2EH purification step in which the crude 2EH is purified to a desired purity to obtain a 2EH product. The purification of crude 2EH is conducted mainly by distillation.
Although it is a matter of course that alcohols including 2EH as industrial products which are dealt in on the market should have a high purity, these alcohols are also required to be reduced in coloring in a sulfuric acid coloring test.
Substances which have been conventionally known to cause 2EH to give unfavorable results in a sulfuric acid coloring test are aldehydes such as 2-ethylhexanal (2HA) and unsaturated alcohols such as 2-ethylhexenal. For example, patent document 1 discloses a process for producing a saturated alcohol by reacting the corresponding aldehyde in a vapor phase with hydrogen, wherein a product of the reduction of a catalyst precursor composition containing an ingredient represented by the following general formula (i) is used as a hydrogenation catalyst to thereby diminish unsaturated alcohols in 2EH.
[Formula-1]Cu(a)-Cr(b)-Zn(c)-Mn(d)-Ba(e)-X(f)  (i)(In the formula, X represents a transition metal in Group 8 or Group 4A of the periodic table, and a to f, which represent the contents of the respective components in terms of oxide amount, are as follows: a indicates 20-50% by weight, b 0-50% by weight, c 0-50% by weight, d 0.1-5.0% by weight, e 0.1-5.0% by weight, and f 0.01-3.0% by weight.)
However, there are cases where even 2EH from which aldehydes and unsaturated alcohols have been removed gives poor results in a sulfuric acid coloring test.
Patent Document 1: JP-A-8-3084